对流换热过程的热力学优化与传热优化

为了进一步明确对流换热过程中热力学优化与传热优化之间的差异,本文分别利用熵产最小原理、(火积)耗散极值原理针对两种边界条件下的对流换热问题进行分析,讨论熵产,(火积)耗散与有用能损失以及对流换热能力之间的关系.结果表明:熵产最小意味着系统的有用能损失最小,但并不反映系统的对流换热能力的强弱;而(火积)耗散取极值意味着系统的对流换热能力最强,但与系统的有用能损失不存在对应关系.因此,对于将降低有用能损失作为优化目标的换热问题应采用熵产最小原理进行分析;而对于需要将提高换热能力作为优化目标的对流换热问题应采用(火积)耗散极值原理进行分析.

THERMODYNAMIC OPTIMIZATION AND HEAT TRANSFER OPTIMIZATION FOR CONVECTIVE HEAT TRANSFER

In the interest of illuminate the differences between the thermodynamic optimization and the heat transfer optimization,a convective heat transfer process with two types of thermal boundary conditions was studied and the relationship between entropy generation,entransy dissipation, exergy loss and heat transfer performance was analyzed.Numerical results show that the minimum entropy generation means the minimum exergy loss,while the extremum entransy dissipation means the best heat transfer performance.Therefore,for heat transfer optimization with different objects, the minimum entropy generation principle should be used to reduce exergy loss,while the extremum entransy dissipation principle should be used to enhance heat transfer performance.